BACKGROUND To improve process design, and scale‐up of gas biofilters, a thorough understanding of compounds degradation mechanisms within model engineering biofilters is needed. The aim of this study is then to investigate the spatial distribution of pollutants removal within an experimental semi‐industrial biofilter fed with industrial emissions from a rendering plant. RESULTS A stratification pattern of pollutants removal has been highlighted: nitrogenous compounds, esters, volatile fatty acids (VFA), alcohols, ketones and aldehydes are completely or mostly removed especially in the biofilter layers near the gas inlet. In return, the removal of sulphur compounds seems to begin when nitrogenous and oxygenated compounds are almost fully degraded. A sequential degradation of sulphur compounds is also observed: hydrogen sulphide is eliminated in the biofilter section near the gas inlet while methylmercaptan (removal efficiency 87%) and dimethyl disulphide (DMDS) (removal efficiency 73%) are mainly eliminated in the second half of the column. CONCLUSION An on‐site semi‐industrial biofilter used for waste gas abatement in an animal‐rendering plant exhibited spatial distribution of the compounds removal efficiency. The removal of organic sulphur compounds is not complete. Hence, this work emphasizes the importance of improving gas biofilters to achieve complete elimination of pollutants causing unpleasant odours. © 2014 Society of Chemical Industry

New emerging issues appears regarding the possible aerosolization of micro-organisms from biofilters to the ambient air. Traditional bioaerosol sampling and cultural methods used in literature offer relative efficiencies. In this study, a new method revolving around a particle counter capable of detecting total and viable particles in real time was used. This counter (BioTrak 9510-BD) uses laser-induced fluorescence (LIF) technology to determine the biological nature of the particle. The concentration of viable particles was measured on two semi-industrial pilot scale biofilters in order to estimate the Removal Efficiency in viable particles (REvp) in stable conditions and to examine the influence of pollutant feeding and relative humidification of the gaseous effluent on the REvp. The REvp of biofilters reached near 80% and highlighted both the stability of that removal and the statistical equivalence between two identical biofilters. Pollutant deprivation periods of 12 h, 48 h and 30 days were shown to have no influence on the biofilters’ removal capacity, demonstrating the robustness and adaptation capacities of the flora. In contrast, a 90-day famine period turned the biofilters into emitters of viable particles. Finally, the humidification of the effluent was shown to negatively influence the removal capacity for viable particles, as drying off the air was shown to increase the REvp from 60 to 85%.

Total polar compounds before (retentate) and after (permeate) application of the new membrane filtration system.